Bumper structures including a recessed opening formed in a top center portion in a vehicle width direction of an impact absorption member which is attached on a front surface of a front bumper beam have been disclosed.
For example, in bumper structures disclosed (especially depicted with figures) in Japanese Unexamined Patent Application Publication Nos. 2007-182162 and 2008-056081, a protruding portion is formed in a top center portion of an impact absorption member in a vehicle width direction, and the protruding portion is depressed into a triangular shape so as to fit the shape of a front grill.
In a bumper structure disclosed in Japanese Unexamined Patent Application Publication No. 2006-213105, an impact absorption member is formed so that the cross section of a center portion of the impact absorption member in a vehicle width direction has a smaller height and thickness than the cross sections of ends of the impact absorption member in the vehicle width direction, and there is a space between a front surface of the impact absorption member and a bumper face.
In a bumper structure disclosed in Japanese Unexamined Patent Application Publication No. 2010-042783, two ribs are formed on a top surface of an impact absorption member, and an opening is formed between these ribs.
However, in the case where the bumper structures described in Japanese Unexamined Patent Application Publication Nos. 2007-182162 and 2008-056081 are employed, when a vehicle collides with the other vehicle having a height greater than that of the vehicle, there will be an unsquashed portion of the impact absorption member of the vehicle sandwiched between the bumper of the other vehicle and the bumper beam of the vehicle. When there is an unsquashed portion, a downward moment is produced due to a difference in the amount of squash between the top and bottom portions thereof. The downward moment causes the impact absorption member to slide downward, and as a result, a phenomenon called underride in which the vehicle runs underneath the other vehicle occurs. When the underride occurs, the bumper structures may not be able to appropriately absorb a collision load.
On the other hand, in the case where the bumper structures described in Japanese Unexamined Patent Application Publication Nos. 2006-213105 and 2010-042783 are employed, since an opening is formed in the top center portion of the impact absorption member of the vehicle in the vehicle width direction, the bumper of the other vehicle collides with the bumper beam via the opening when the vehicle collides with the other vehicle having a height greater than that of the vehicle. Thus, only a small portion of the impact absorption member is squashed, and the underride does not occur. However, there is a problem that since only a small portion of the impact absorption member is squashed, a load will not be distributed by the impact absorption member, and the collision load will concentrate in a limited area in the vicinity of the center of the bumper beam. As a result, the collision load will not be appropriately absorbed.